For achieving a high measuring accuracy, it is necessary to calibrate measuring devices, for example vector network analyzers. To perform such a calibration, successively, a number of calibration standards are connected to the measuring ports of the measuring device. After the calibration measurements are complete, the measuring device is calibrated based upon results of the calibration measurement.
When using a calibrated measuring device, in the ideal case, measured values are identical to the actual value. In practice, however, a number of effects lead to remaining measurement uncertainties. Further, the user is unaware of the existence or value of such measurement uncertainties when performing measurements with, what is believed to be, a calibrated measuring device, which is disadvantageous, since the user could rely on measuring results which actually are far less accurate than expected.
The document U.S. Pat. No. 8,612,177 B2 shows a measuring device which tries to mitigate the above-described problem by theoretically calculating a measurement uncertainty and displaying it along with measuring results. The calculated measurement uncertainty though is very inaccurate and does not take the individual measuring device and measuring setup into account. The user therefore cannot rely on the displayed measurement uncertainty. On the one hand, the actual measurement uncertainty might be significantly lower than displayed, which leads the user not to trust the measuring results. On the other hand, the displayed measurement uncertainty might be too low. This leads the user to falsely trust the measuring results although the actual measurement uncertainty is larger.
What is therefore needed is a calibration approach for a measuring device, such as a vector network analyzer, that eliminates measurement uncertainties.